When a document is placed on a scanner platen, the document may be placed at an angle relative to the direction of the scan. In this situation, the document content may be skewed, also considered rotated, in the scanned document page, also considered the document image or the image. Document-content skew may also arise when a document is scanned using an automatic document feeder. Additionally, content in an image may appear skewed relative to the image boundaries due to document layout attributes. That is, content may be rotated relative to an image boundary for stylistic or other reasons.
An accurate estimate of a skew angle associated with a document image may be required for many reasons. For example, some image-processing techniques may require accurately determined content boundaries for which knowledge of the document skew angle may be necessary. Furthermore, a scanning system that supports automatic skew detection and skew-angle determination may be desirable since they may be crucial to the scanning system's ability to automatically handle an arbitrarily placed document. Efficient skew estimation may be desirable for devices with limited computational resources.